Fuel injection valve and method of manufacturing the same

A fuel injection valve comprising:

• a unitary pipe made of a composite magnetic material including a ferromagnetic fuel connector portion disposed at one end thereof, a ferromagnetic valve body portion disposed at the other end thereof and non-magnetic intermediate pipe portion disposed between said fuel connector portion and said valve body portion;
• an electromagnetic solenoid disposed outside said unitary pipe around said intermediate pipe portion;
• a needle valve disposed inside said unitary pipe at said valve body portion;
• a magnetic stationary core disposed inside said unitary pipe at a portion of said intermediate pipe portion and also extending along al least a portion of said fuel connector portion to provide a surface receiving magnetic flux from said fuel connection portion;
• and
• a magnetic movable core disposed inside said unitary pipe to face an axial end of said stationary core through a magnetic gap and fixed to said needle valve to form a magnetic circuit for said solenoid together with said fuel connector portion, said stationary core and said valve body, and to be slidable on the inner periphery of said valve body portion.

A fuel injection valve comprising:

• a unitary pipe composed of a magnetic fuel connector portion at one end thereof, a magnetic valve body portion at the other end thereof, and a non-magnetic intermediate pipe portion between said fuel connector portion and said valve body portion;
• an electromagnetic solenoid disposed outside said unitary pipe around said intermediate pipe;
• a magnetic stationary core disposed inside said unitary pipe to extend axially to provide a surface sufficient to receive magnetic flux from said fuel connector portion;
• a magnetic movable core disposed to be magnetically spaced apart from said stationary core inside said unitary pipe to form a magnetic circuit for said solenoid together with said fuel connector portion, said stationary core and said valve body portion,
• wherein said unitary pipe is made of material that can be changed from magnetic material to non-magnetic material.

A fuel injection valve comprising:

• a generally straight and smooth unitary pipe composed of a martensitic fuel connector portion at one end thereof, a martensitic valve body portion at the other end thereof, and an austenitic intermediate pipe portion between said fuel connector portion and said valve body portion;
• an electromagnetic solenoid disposed outside said unitary pipe around said intermediate pipe;
• a magnetic stationary core disposed inside said unitary pipe to extend axially to provide a surface sufficient to receive magnetic flux from said fuel connector portion;
• a magnetic movable core disposed inside said unitary pipe to form a magnetic circuit for said solenoid together with said fuel connector portion, said stationary core and said valve body portion.

A fuel injection valve comprising:

• a unitary pipe made of a composite material capable of being selectively made to have ferromagnetic properties or not to have ferromagnetic properties;
• said pipe having an intermediate portion not having ferromagnetic properties located between first and second portions having ferromagnetic properties;
• an electromagnetic solenoid disposed outside said unitary pipe at said intermediate portion and extending along at least part of said first and second portions;
• a needle valve disposed inside said unitary pipe at said second portion;
• a stationary ferro-magnetic core disposed inside said unitary pipe at said intermediate portion and extending along a part of said first portion to provide a surface receiving magnetic flux from said first portion;
• and
• a movable ferromagnetic core disposed inside said unitary pipe to face an axial end of said stationary core through a magnetic gap and fixed to said needle valve to form a magnetic circuit for said solenoid together with said first portion, said second portion, and said stationary core while being slidable on an inner periphery of said second portion.